Done well, I love these things more than pretty much anything else in the world. Lemme show you what I mean.

Evangelion's somewhat mediocre opening (I'm told it was groundbreaking, but it's really not very fun to watch. Hey, just like the rest of the series! :awesome:) redone into pure awesomeness as a Stone Ocean opening.

Bleach's (amazing) first opening, redone as Baccano! To great effect.

SO, UH. MY LOVE FOR THESE THINGS CANNOT REALLY BE EXPLAINED, I JUST LOVE THEM.